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338                        STELLER'S SEA-COW

complete skeleton. The skull is like that of other Sirenia, with
the down-turned, premaxillary region. But the nasal bones, lost,
or at least rudimentary, in recent forms, are well developed; the
likeness of ancient to living forms in this respect "being exactly
paralleled by the Zeuglodonts, when compared with recent "Whales.
The vertebral centra exhibit distinct epiphyses, which have dis-
appeared in living Sirenians. The cervical vertebrae are seven, of
which the second and third are occasionally fused. There are
nineteen pairs of ribs, and there are three lumbar vertebrae.
The sternum consists of three separate pieces. There is a
rudimentary femur.
The recently-extinct Steller's Sea-cow, belonging to the genus
Hhytina, was a huge beast, seen in the flesh up to nearly the end
of the last century. It frequented the shores of Bering's Straits.
Its remains occur in the peat on the shores of those seas. It reaches
a length of some 20 to 30 feet. The external characters were
much like those of other recent Sirenians. The nostrils were above
the fore part of the snout, the latter being truncated and obtuse.
The tail was of the Cetacean pattern, and thus like that of Halicore.
The head of this Sirenian was small, and the teeth had entirely
vanished save for the apparent existence as transitory structures
of two small incisors in the upper jaw. The absence of teeth
was compensated by the presence of a horny palate for the
trituration of the sea-weeds which constituted the food of Steller's
Sea-cow, The fore-limbs seem to have possessed no nails, but
were covered at the extremity with short, bristly hairs, no doubt
serving the purpose of keeping the animal moored in safety to
the slippery beds of Fueus upon which it browsed.
There are nineteen pairs of ribs. The vertebrae of the
cervical region are the customary seven, and the centra are thin
and plate-like as in the Cetacea, the animal being thus short-
necked like those marine creatures,